The Hopkins Population Center (HPC) is a multidisciplinary population research center established in 1971, and awarded its first Center grant in 1972. The purpose of this proposal is to request continuing support for the Center's six core units. The Administrative Core is responsible for overall policy direction and planning for the HPC, for administrative coordination of research cores, and for promotion of population research and attention to population issues throughout the Johns Hopkins University. The Computing Core provides a range of computing and programming services to Center Associates, and is responsible for the planning and organization of services so as to be responsive both to Associates' computing requirements and to a rapidly changing computer environment. The Mathematical and Statistical Services Core provides Center Associates with ready access to four highly skilled statisticians for advice on all aspects of population research. The Information Unit maintains the Population Center Library Collection, provides a range of information search and retrieval services for Center Associates, and distributes Center working papers and reprints. The Electron Microscopy Core maintains an electron microscope and supporting equipment, and provides Associates with ready access to inexpensive electron microscopy services, ant to expert advice. The Radioimmunoassay Core provides similarly inexpensive facilities to Center Associates for the performance of radioimmunoassays. These six cores will provide services to 36 projects in demography/reproductive health and reproductive biology. A total of 40 University faculty members are affiliated with the HPC, as Associates, staff, or members of Advisory groups. These faculty represent 13 departments and four University divisions (Hygiene and Public Health, Arts and Sciences, Engineering, and Medicine). The substantial contributions of Hopkins investigators to population research are described in this proposal, and are reflected in the well over 500 publications that have appeared since the last Center review. The support for the HPC requested in this proposal will enable us to continue that record of productive research.